E+e− Physics at CESR

Abstract

The study of high energy electron positron interactions has, in the past decade, provided us with a wealth of experimental information about all aspects of particle physics. The charmed quark, or c-quark, was simultaneously discovered in hadron interactions and in e+e− annihilations. It was however mostly at e+e− colliders that its properties were (and still are) investigated. The measurements of the annihilation cross section into hadrons has given tangible evidence about the existence of color and the continued study of these processes at high energies has confirmed many qualitative predictions of Quantum Chromo Dynamics (QCD), the best candidate at present for a complete theory of the strong interactions. The discovery, in hadron collisions, of the upsilons in 1978, required the existence of yet another quark, the b-quark, where b stands sometimes for beauty or bottom, a new flavor of quarks. Because of its large mass, ∿ 5 GeV, the b quark has greatly helped in clarifying many aspects of strong interactions, especially in the spectroscopy of heavy particles. The study of the b quark, carried out only at electron positron colliders, has given new proofs that quarks carry color and fractional charge (1/3e for the b quark) and that gluons exist, have spin 1 and carry color, as required by QCD. In the field of weak interactions further proof of the validity of the “standard model” has been obtained and strong constraints on the mixing angles have been established. In the last three years most of the study of the b quark has been carried out at the Cornell Electron Storage Ring, CESR, because of a fortunate set of circumstances. In these lectures I will present what we have learned from this study at CESR [1], where the focus has been and continues to be on the T resonances [2,3], from which we learn about heavy quark spectroscopy, and on the weak interactions of the b-quark, through the study of B-meson properties.KeywordsDecay ChainQuantum Chromo DynamicsBranch RatioMeson DecayThrust AxisThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.